There probably is a way, but that wouldn't change much. Reaction shoot would miss in 90% of cases.That would also hurt the balance for melee gals since they rely on not being hit too hard. Enemies with weapons like rocket launcher would decimate themselfs and them, while creatures like Zombies and Chrystalisks would make those gals useless.

We know the mod ATM only allows snapshot to reaction. You could just take away the snap function from rocket launchers and replace with surefire with a burst of 1. You could do this with a variety of weapons but leave the snap on certain things like swords to reflect parry /riposte.

Reactionable melee would be a huge shift in balance, guns would still be largely worthless since cqc check would remain. But Zombies and Chrysalids would be too threatening to ever engage. Also using melee to soften tanks would be drastically limited, since some tanks can still kill the gal with a miss.

Code already allow reaction to melee attacks. Only for backward compatibility its not active. Scripts can alter this behavior to enable reaction.This mean you can encode if you are kung-fu masta nobody can react to your attacks.